1. Field of the Invention
The invention concerns a wind power installation and in particular electrostatic discharge protection of such wind power installation.
2. Description of the Related Art
Wind power installations of modern type, for example one of type E-40 or E-66 from Enercon are usually equipped with a lightning protection system which is known for example from DE 44 36 290, DE 198 26 086, DE 195 01 267, DE 44 45 899, WO 00/14405 or WO 96/07825.
In the case of such lightning protection systems like the known systems described hereinbefore, when the rotor blade is galvanically separated from the hub the respective rotor blade can be statically charged up. That electrostatic charging of a rotor blade occurs due to the friction of the air against the rotating rotor blade of a rotor of a wind power installation. Depending on the respective air humidity or other disadvantageous weather influences the rotor blades (or the lightning protection systems thereof) charge up more quickly or more slowly. Static charging occurs until the flash-over voltage of the air gap is reached. Flash-over then takes place and the entire system or the rotor blades are discharged. Such a flash-over produces electromagnetic waves (EMC) with an extremely high band width because the flash-over occurs virtually in the form of a pulse which ideally has an extreme band width (ideally an infinite band width). These abrupt discharges which are not due to a lightning strike because of a storm but due to electrostatic charging of the rotors interfere with the entire electronic system of the wind power installation, which is in the area around the flash-over, such as for example the computers or microprocessors which control and regulate an individual rotor blade. However other electronic devices of the wind power installation are also affected, which are disposed in the pod or in the proximity of the spark flash-over path. Charging of the rotating rotor blades regularly involves flash-over effects at the spark gap with likewise regular interference with the electronics, which however is not desirable for protection of the entire electronic installation devices.